N.Y.).One Sentence Summary: Detailed single-cell phylogenies capture the frequency, tissue routes, and seeding patterns of metastasis in vivo.
Abstract:25 2 Consequential events in cancer progression are typically rare and occur in the unobserved past. Detailed cell phylogenies can capture the history and chronology of such transient events -including metastasis. Here, we applied our Cas9-based lineage tracer to study metastatic progression in a lung cancer xenograft mouse model, revealing the underlying rates, routes, and patterns of metastasis. We report deeply resolved phylogenies for tens of thousands of metastatically disseminated cancer cells. We observe surprisingly diverse metastatic phenotypes, 5 ranging from metastasis-incompetent to highly aggressive populations, and these differences are associated with characteristic changes in transcriptional state, including differential expression of metastasis-related genes like IFI27 and ID3. We further show that metastases transit via tissue routes that are diverse, complex, and multidirectional, and identify examples of reseeding, seeding cascades, and parallel seeding topologies. More broadly, we demonstrate the power of next-generation lineage tracers to record cancer evolution at high resolution 10 and vast scale.
Main Text:Cancer progression is governed by evolutionary principles (reviewed in (1)), which leave clear phylogenetic signatures upon every step of this process (2, 3), from early acquisition of oncogenic mutations (i.e., the relationships between normal and malignantly transformed cells (4)), to metastatic colonization of distant 15 tissues (i.e., the relationship between the primary tumor and metastases (5)), and finally adaptation to therapeutic challenges (i.e., the relationship between sensitive and resistant clones (6)). Metastasis is a particularly important step in cancer progression to study because it is chiefly responsible for disease relapse and mortality (7). Yet because metastatic events are intrinsically rare, transient, and stochastic (8,9), they are challenging to monitor in real time. Analogous to the cell fate maps that have played an essential role in deepening our understanding of 20 organismal development and cell type differentiation (10, 11), accurately reconstructed phylogenetic trees of tumors and metastases can reveal key features of this process, such as the clonality, timing, frequency, origins, and destinations of metastatic seeding (12).Lineage tracing techniques allow one to map the genealogy of related cells, providing a critical tool for exploring the phylogenetic principles of biological processes like cancer progression and metastasis. Classical